Mast



Jan. 8, 1952 I BLACK 2,581,351

MAST

Filed Feb. 21, 1946 4 Sheets-Sheet l INVENTOR.

ERIC A. BLACK ATTORNEY Jan. 8, 1952 Filed Feb. 21, 1946 E. A. BLACK MAST4 Sheets-Sheet 2 l/3O K 94 INVENTOR.

ERIC A. BLACK 13y L "/-'e/4'M g, A

ATTORNEY Jan. 8, 1952 E. A. BLACK 2,581,351

MAST

Filed Feb. 21, 1946 4 Sheets-Sheet 3 INVENTOR.

ERIC A. BLACK ATTORNEY E. A. BLACK MAST Jan. 8, 1

4 Sheets-S 4 Filed Feb. 21, 1

I WM M lllllm lllllllr INVENTOR. ERIC A BLACK ATTORNEY FIG.8

Patented Jan. 8, 1952 UNITED STATES PATENT OFFICE MAST Eric A. Black,Red Bank, N. J. Application February 21, 1946, Serial No. 649,450

(Granted under the actof March 3, 1883, as

12 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

The present invention relates to masts. v

In the erection and use of various braced compression members, includingmasts or towers, particularly of the portable type, such as for radioantennas and the like, it is desirable that the parts have lightnesscoupled with suificient structural strength to resist the stressesincident to erection and use. Although the present invention isparticularly well adapted to portable radio towers and .it will beillustrated in connection therewith, it is to be understood that theinvention has considerably wider application.

Conventional portable masts and the like are usually sustained by aplurality of guys. In sustaining such masts great care must be takenduring erection to avoid rupture of the central mast member. In manycases it has been found necessary to make the central mast memberconsiderably oversized and overweight so that it may withstand therigors of erection.

If a mast is of the portable type it is ordinarily desirable that it beseparable into convenient units to facilitate transportation andhandling. Difficulties have arisen in connection with providing suitablecoupling means to join said units into an integral structure. Oversized,overweight and complicated parts are a handicap to portability.

The present invention is intended to provide means and a method ofconstruction for masts and the like and also a means of erection whereinsimple, relatively inexpensive parts, of less weight and smaller size,may be utilized for structures which may be separated into easilymanaged units, which may be simply and quickly erected, and which havesufficient structural strength and stability to provide the desiredsafety factors.

It is therefore an object of the present invention to provide a mast orother structure which may be fabricated of lightweight materials, suchas aluminum.

It is a further object to provide such a mast which may be assembled ofa plurality of units, each of which may be of a size and weight suitablefor portability.

It is still another object to provide simple means for giving such amast suficient structural strength to allow it to be easily and safelyerected and to enable it to withstand windage, loads and other stressesinvolved in its use.

It is a further object to provide means for prestressing the elements ofa mast so as to give it the requisite structural strength and stability.

It is still another object to provide means for applying tension tobrace members without the use of turnbuckles or the like thereon.

. .Yet another object isto provide a means for amended April 30, 1928;370 O. G. 757) 'of post section spliced together.

2 It is still another object to provide a construction for masts and thelike which requires a much smaller number of guys and anchor means thanconventional structures.

It is still another object to provide a mast wherein stresses within theparts are far better equalized than in conventional structures utilizinga plurality of sets of guys fastened at different levels.

It is another object to provide a construction for masts and the likewhich is triangular in cross section and thereby has greater sturdiness,strength and stability than conventional quadrilateral structures.

It is yet another object to provide a mast and the like wherein erectionmay be accomplished without the use of auxiliary gin pole devices.

The foregoing objects and others, which will become clear from thepresent specification, are accomplished by providing a structure for amast or the like which includes a central post, which may be made up ofa single post or a plurality Said mast is given rigidity and strength bymeans of a plurality (preferably three) of brace members which aresecured, at their opposite ends, to the post and are forced outwardly,at their central portions, so as to be put under suitable tension, by

means of strut members. Said strut members are made adjustable ineffective length in a manner somewhat similar to a conventionalumbrella.

Each strut member incorporates a stiff strut I having its outer endpivoted to the central portion of a brace member and having its innerend pivoted to a part (hereinafter referred to as a spider) which islongitudinally slidable along the post and is provided with means topivotally connect with the inner end of said strut. During assembly ofthe components the said strut is disposed at an angle of somewhat lessthan to the post. When the spider is moved longitudinally relative tothe post, said angle approaches 90 thus pushing the central portion ofthe brace member outwardly. This subjects the braces to tension and thepost to compression.

A simple tower (as shown in Figures 1A and 8) might includes a twosection post provided with three outwardly extending adjustable strutsand suitable braces. The same principle might be applied to larger mastshaving any number of sections. One such tower made up of four postsections is shown in the accompanying drawings (Figures 5-7).

Said masts are preferably assembled on their sides on the ground and maythen be raised in a number of ways. A simple erecting method, in whichsome of the parts needed for erection are incorporated permanently intothe mast is 60 illustrated in connection with the simple tower aforesaid(Figure 4).

For a better understanding of the invention, together with other andfurther objects thereof,

referenceis" had to the following description taken in connection withthe accompanying drawings, wherein like parts are indicated by. likereference numerals and its scope will be pointed out in the accompanyingclaims.

In the drawings,

Figure l is an isometric view of a simple'form of mast embodying thepresentinvention;

Figure 2 is an enlarged fragmentary perspective view showing details ofthecentral-portion of the mast of Figure 1;

Figure 3 is a further enlarged fragmentary view of the central portionof the mastcf Figure l, the upper portion beingshown in vertical sectiona'n'dth'e lower portion in elevation with parts cut awa for clarity;

Figure 4 is an elevational'viewof the mast of Figure 1 during erection;them as't being shown in solid lines upon the ground and in" brokenlines when about halfway up;

Figure 5' is an elev'ati'oiialv'iew of a more complicated mastincorporating the present invention;

Figure 6 is a fragmentaryenlarged'elevational' Referring'now tothefdrawi'ngs, and more'par-' ticularly' tojFigui'es' 1-3 and 8"thereof, the form of radio antenna mastembodying the present inventionwhich is there shown includes a central post sustained upona base ll".Said central post is made up of have and upper post sections l3,

15, each of which sections comprises'an'elongated'm'etal pipe IT,having" three longitudinally disposed slots I9cut throughit', 120 apart,at one end; The slotted end of" each pipe ll (namely, the upper end ofthe lower post" sec tion I3 and the lower end-of the upper post'sec tioni5) is closed by a" transversely disposedtriangular endplate 21, whichis pierced by a'hole 23 at its midpoint and an inwardly extending slot'at each corner, and which is rigidlysecure'd tothe end of thepipeby'anyv suitable means, such as welding.

Three pairs of spaced" parallel gusset flanges 25 (Figures 2, 3 and 8)-aresecured, as by weld ing, to the'outside' of each pipe t1, so as to extend outwardly from" said pipealong both sides' of each of theslots' l9aforesaid. Each of the flanges 25 is pierced along its length by severalholesZ'I. Thelower and upper post'sectio'ns i3; 15 are aligned with eachother, but with their end plates 2| spaced from each other; and arejoined together by three splice plates'z'a'; each of which is a fiatelongated plate pierced by a hole at each end. Each splice plate29"hasone'enjdf extending between one pair of gusset flanges 25 of oneof thepost sections 13, i5 and bolted thereto by a bolt 30, and itsother end similarly bolted to the other of said post sections.

Each pipe H is also provided with a spider- 3! (Figures 2, 3 and 8).Each spider 3f is made" up of a short internally threaded sleeve 33 tothe outside of which are secured three radially disposed legs 35. Saidlegs 35 are rigidly joined to the sleeve'33, as by welding, andare'positioned' 120 apart and each leg is pierced by a parrot holes 39.A short tubular g'uidetl. positioned coaxially with the sleeve 3'3; issecuredto the three" p 4 lgsi35. Each' spider 3i ispositioned coaxiallywithoneof the pipes I! so that the sleeve 33 and guide 31 are positionedwithin said pipe and the three legs 35 extend outwardly through theslots i9 in said pipe. The tubular guide 3? is of a size to makealongitudinally slidable fit within the pipe 11. I

Extending'through the hole 23 in the end plate 2l andthreaded into thesleeve 33 is a hexagonall-y headed spider adjusting bolt ti. Between thehead of thebolt' ll and said end plate 2! is a suitable annular thrustbearing 40, which may be of the Oilite type,.which.is made up of metalimpregnated"with allubricant. A collar 33 encircling? the bolt just:inside the end plate 21 is fastened to said bolt by a cotter pin as.

The heads of the twospider adjusting bolts 4! are provided;respectively, with an axially disposed dowel 45 and witlij an axialcavity 4?, receivable to saiddowelf fi; so thatsaid'bolts maybevpositioned coaxially." head to' head for inch--vidual"operationalrotation. Itwillnow be seen that,.upon rotationofeither one of the spider adjustingibolts 4I,,the'spider'3|, in threadedengagement with'it, is caused tomove longitudi nally relativeto'the'pipe IT;

The lowerextremity'of the lower post section 13' and the'upper'extremity of the upper post section !5 are'e'ach fitted withthree pairsof outwardly extending spaced parallelgusset plates 39 which are"respectively aligned with the pairs of gusset flanges25" at'the otherends of said post sections. The lower end of the-lower post' sectionl3'is rigidly joined to the T-shaped base I I by means'o'faj basebracket 53;

The T-shaped base is madeup of a stem- 55 and a cross member 51, both ofwhich are preferably made of metal pipe, one end of the stem 55 beingsecurely "joined perpendicularly to the cross member 51 at its midpoint,by any suitable'means, such'as welding, or preferably by a suitableseparable bracket (not shown) to allow said stem 55 and cross'me'mber 57to be disconnected for transportation. A' pair of short tubular crossmember extensions 58 are rotatably coaxially joined to the extremitiesrespectively of the'cross in'emberfl" by Ineans'of pipes 68 of slightlysmaller diameter, which are rigidly se-- cured to said'cross memberextensions 58 and are rotatable relative to the cross member 5'1;

The stem 55; near'its outer end, and each of said cross memberextensiorisBBis pierced by a' transverse" anchor opening 64- receivableto the upper end'of aground anchor 62of any suitable of metal pipe ispivptally secured to the outer end of each of the six legs 35 of the twospiders 3i, thus providing three pairs of spider struts 6t extendingoutwardly from the midportion of the central post, said pairs of spiderstruts 6| being spaced at intervals about the central post. The outerends of each pair of spider struts 5i are'pivo'tably fastened to a strutconnector 63.

Each of the three strut connectors 63 (see Figured) includes aihorizontally disposed, flat strut gusset plate 65" to which arewemecrveal:

cally disposed upwardly and downwardly extending connector fins 61, eachof which fins is pierced by a hole. Two gusset shackles 69 are securedrespectively to said connector fins 61.

Each gusset shackle 69 is made up of a piece of flat metal folded uponitself so as to give it the shape of a U in cross section and itsopposite sides are pierced by four holes in mutual register, one of saidholes being a horizontally disposed slot 19. Each gusset shackle 69 isalso pierced by an elongated fin aperture along its folded portion toallow one of the connector fins 61 to extend therethrough so as to bebolted to said gusset shackle by means of a bolt passing through theslots 16. Said fin apertures are longer than the width of the connectorfins 61 extending through them, to allow adjustment therebetween, aswill be made clear hereinbelow. One of the strut connectors 63 isfitted, either permanently or temporarily during erection, with a metalring 68. Said ring 68 should be to the same side of the post sections|3, |5 as the pulley 66 mentioned above. The three strut connectors 63are joined by three struts 73 which form an equilateral triangle andmaintain the strut connectors 63 in their equally spaced positions. Eachstrut i3 is preferably made of metal pipe, and each of its ends isslotted and bolted directly to one of the strut gusset plates 65.

Three lower braces I5, also preferably made of metal pipe, are bolted,at their lower ends, respectively to the gusset plates 49 at the lowerend of the lower post section l3 and, at their upper ends, respectivelyto the three lower gusset shackles 69 of the three strut connectors 63.Three similar upper braces 11 have their upper and lower ends similarlybolted respectively to the gusset plates 49 at the upper end of theupper post section I5 and to the upper gusset shackles 69 of the strutconnectors 63.

Three guys 19, which are also preferably made of metal pipe, have theirupper ends pivotally secured respectively to the lower gusset shackles69 of the strut connectors 63 and their lower ends secured respectivelypivotably to guy bolts 8| which extend downwardly through holes in theupper ends of the erection connector arms 59 and are connected thereto(during erection of the mast) by adjusting nuts. The lower ends of saidguy bolts 8|, (when the mast is in its erected position) are securedrespectively to three ground anchors 62 through suitable adjustablemembers, such as turnbuckles 83.

A radio antenna 85 (indicated by broken lines) may be sustained upon theupper end of the upper post section l5 in any suitable way and may bemaintained thereon by three antenna braces 81 (also indicated by brokenlines), preferably of metal pipe, secured at their upper ends to saidantenna and at their lower ends respectively to the upper gussetshackles 69 of the strut connectors 63.

As shown in Figure 4, in order to erect the antenna mast described above(Figures 13 and 8) some additional equipment is necessary. Thisadditional equipment includes a conventional chain hoist 89 whichincludes a loop 9| of chain by which it is operated and two single ends93, 95, one of which is shortened while the other is lengthened uponoperation of the said loop 9|. Also required are a large coil sprin 91and an auxiliary ground anchor 62a which is used only during erectionand is not needed to support the mast after erection.

The mast just described (Figures 1-4) may be raised in variousways.Howeverpa preferrederection method, and a method for which certain.components of the mast were specifically designed, will now Figure 4.

The base H is first placed horizontally upon the ground in the positionit is to occupy when the tower is erected. Using said base as a templatea marker is placed in the ground below each anchor hole 64,. The base His then removed and three ground anchors 62 are sunk into the ground atthe three places so marked. The base i! is then replaced in the positionwhich it will finally occupy, so that the three ground anchors 62respectively extend upward through the three anchor openings 64.

The fourth auxiliary ground anchor 62a is then sunk into the ground at apoint aligned with the base stem 55 and distant from the cross member5'l a distance equal to approximately one-half of the height of thefinished tower, so that the three anchors 62 and the auxiliary anchor62a will delineate the four extremities of a cross upon the ground. I

The upper and lower post sections |3, |5, while on the ground, are thenpositioned end to end so that the dowel 45 on the head of one of thespider adjusting bolts 4| fits into the axial cavity 5? in the head ofthe other spider adjusting bolt 4|. The three splice plates 29 are thenslipped into the openings between the flanges 25 be described inconnection with of the lower and upper post sections I3, l5. The

opposite ends of said three splice plates 29 are then boltedrespectively to the three pairs of flanges 25 of the lower and upperpost sections I3, I5. The outer end of the base stem 55 is then swungupwardly, the cross member 51 pivoting about its axis during thisoperation, untilthe base takes the position shown in Figure 4. The lowerend of the lower post section I3 is then raised to the position shown inFigure 4 and secured to the base II by means of the base bracket 53.

The spiders 3| should be so positioned at this time that the legs of theupper spider are in register with the uppermost hole of the flanges 25of the upper post section 15, and the legs 35 of the lower spider 3| arein register with the lowermost holes of the flanges 25 of the lower postsection |3.- The six struts 6| are then bolted to the outermost holes 39of the six spider legs 3| and the other ends of said struts are boltedrespectively to the six gusset shackles 69 of the three strut connectors63. The lower and upper braces 15, H are then bolted into place betweenthe strut connectors 63 and the gusset plates 49 andthe guys 79 arebolted to the strut connectors 63 at one endand to the erectionconnector arms 59 at the other.

The spider bolts 4| are now rotated by means of a wrench so as to bringthe spiders 3| toward each other. While this is being done the bolts Hmust be loose so that the gusset shackles 69 can slide outwardly whilethe strut gusset plates 65 and their connector-fins 61 remainstationary. When the arms 35 of the two spiders 3| are so positionedthat the inner holes 39 thereof are in register with the middle holes2'! of the flanges 25, they are bolted in place. The bolts 1| may thenbe tightened to secure the strut gusset plates 65 respectively to theirupper and lower gusset shackles 69.

The chain hoist 89 is now attached to the ring 68 which is attached tothe uppermost strut connector 63 as the mast rests on its side. The freeend-93 of the said hoist 89 1s brought over ensam the pulley '66: andidown. to the ground: anchor; 62 (to-:th'e right in Figural- 4) whereitzistmade'i fast. The other end 95 fiisaid chain hoistl89 connected tothe spring 91, the otheinendnof which is made fast to the; auxiliary?ground anchor 62a.- The 2100p 91 L of: the hois't :89 .isxnow pulled in:the direction which I. will: shorten.. the end s3 and lngthentheetxddflr As :this-xis idoner'. the upper end of the mast will begin=to1 rise: and: the entire mast-structura will pivot? about the: axis-ofthe cross member- 51; saldicrosamember rotating about the-pipes 681Whenthe mast has been swung. up; to: as. suitable working-- level,- theantennas-85 and an,- tenna braces 83 may be secured iii-2place,w-here.-- upon the erection of i: the: mast by means -i of r" the chainhoist 59- may beresumedluntil the post. sections-i3, Hi areverticali Theanchor fii (to the right inF-igure 4J willv then have passed: throughthe anchor opening fi l' inzthe stemr55.

It willbe noted that during erection the lower: ends of the guys 9-are-helcl in place by theereotion connector arms 59. Assoon-as:th'emast'is erect, however; the guy bolts B-I- aresecured to the-anchors 62- through the turnbucklesflii and are suitably tensioned thereby; Thearms 59'may then either be left in'place or removed; asdesired, as-theyare only needed durin erection or dis-- nrantling of the mast. The chainhoist-89; spring- Q'I i and auxiliary anchor 62% (to the left inFigurea) may also be removed.

It will be seen that the tightening of the spiders 31; as describedabove; will'causesuitable tension of the braces l; l'I-and compressionofithe pipes H; but will subject the'struts- I3 to no" strain at-all asthe strut gusset platesSS to which theyare secured, are not movedoutwardly during-the prestressingoperation.

The nest described (Figures- 14 and- 8') may be sustained by but threeguys I9 and ground anchors 62; whereas comparable masts of con ventionaldesign are rectangular so as 'to require atleast four guys and" fouranchors and more likely requirea multiple of four guysand anchors, saidguys going up tosteady themastsatdifferent levels. For example, aconventional mast known to the applicantrequires sixteen guys andanchors, and two auxiliary anchors needed during erection, makingeighteen anchors in all, whereas amast embodying the-present invention,of like size and usefulness; requires but three anchors; and oneauxiliary anchor for erection, making four in all. Thus'th'ere isa greatsaving in expense and" labor. Also addi tional erection equipment,comprising gin poles and the like, areneeded-toraise a-conventional mastWhereas it may be dispensed with in erect ing the mast described above.

A modified form of'antenna' mast embodying the present invention isshown imF-igures 5-7'; Said mast is constructed soas to utilize thesameprinciples as in the simple mast already de scribed, but is preferablyusedin a mast of larger size or ina mast ofsimilar size'but whereinsmaller component parts =-a1e provided to facilitate portability.

Saidzmodified form of mast is madeup of a centralpost comprisingfourpostsections. IIH', I62; I03; I04, whichare similar: tothe postsections- [3, I5 alreadydescribedinconnection with the simple mast(Figures 1-3),,excep t that the intermediate post sections. I 02', I 0-3are:- provided withslots- I9. and spiders 31 a-trbothzends. The; twolower post sections I0 I and I02; are. spliced a-.strut:.systemi as?already described; and: shown: in connection with .thersimple formof:mast1(llig -1 mesa-1+3 and;8)-.. Thus. saidpost sections IIJI;. I 02are joined by; three splice. plates: 29 andtheir strut:spiders;3l are.joined tozthreestrut: conmotors-163 M. meansof six'spider strutsifiL.The: twomppenpostsections 03,104 are alsojoined: toceachother. .inexactly the same way:

The; two; intermediate post. sections; "12,. I03

howeven'. although. joined. together by; similar:

splice plates. 25:, are. providedwith.amorecome pli'cated strut system(see Figures; Gand '7) Said; strut'lsystem includes three. inner:- strutconnece tors I: and three. outer.strutconnectors: III'I.

i Each inner-strut.connectoixI 95.;comprises an inner.

3-2 and downwardlyextendingLflat connectonfins ill I and also:piercediby: two. holeson each side re-- ceivable to.v the inner strutsvH5 and theintermediate struts iii; Each of the inner. gusset: shacklesH3. is U-shaped in cross section, the: arms being piercedby four holesinregister, one: of i which holes is a horizontally disposed slotHill-for slidable coupling to a connector fin :H I. Eachshackle II3 isalso pierced along its folded portion by an elongated fin aperture toslidably. receive one or the connector fins I I I.

Theinner strut connectors 495 are pivotally joined respectively to thelegs35 of the spiders 31 hy pairs of spider struts fil-as already tie-'-scribed above in connection with the simplertower-(Figures 1-3 and 8).

Each inner strut connector IUiikis rigidlyjoined to-one'of the outerstrut connectors I 81 by means oi arpair-of=horizontally disposedextension struts 22 i. E'achextension strut is preferably a-length ofmetal pipe rigidly secured at one end to-oneof 'tlie inner gussetshackles I I3and at theother end' to an outer gusset shackle I23.- Eachof'theouter gussetsliackles I23 is U-shaped-in cross" section;is-pierced al0ng its folded-portion by an elongated fin'aperture, andits=arms=are pierced by five holes in register, one of which holesisslot- I25; bywhich said shackle I23 may-be slidably joinedto an outerstrutgusset plate I21, which-is a horizontally-disposed flat metal platepierced i by two holes and provided with two upwardlyext'ending fiatconnectorfins I29 extend-- inginto said shackles '423 'throughsaidelongated fin apertures in said shackles-123';

The three outerstrut'connectorsltil-are rigidly joined to'each other bythree'outer" struts l3iwhich forma horizontally-disposed equilateraltriangle; Each outer strut I 31- is provided. atits" midpointwith anintermediate strut connector I 33 "to Whichare rigidly connected. theouter ends ofthe' intermediate struts I I I;

Itwill now be seen that, although the strut system (Figures 6 and '7)just described. has more component parts than the. simpler strut system.described previously, the principle of, operation, is exactly the same.

Whenthe various component-parts ofnthe mast. (offFigureii). have beenjoined'together whileon. the. ground. the. spider. bolts M. at theseveral junctions between thepostsectionslfil, I02; I93: and IM'arerotated to. bring the pairs-oispidfirs 3]? toward. each other. The.lowerjunction (betweenpost sections Iilhand; I02) and the upper junction(between post sections:I0-3-. and IIl4-) will operate exactly as:described in connection with together.andare.providedattheir:iunctioniwithr theflsimple mast-(Figures1-3and8);

At the midjunction (between post sections I02 and I03) the adjustment ofthe two strut spiders 3|, however, will cause the two inner gusseshackles N3 of each inner strut connector I05 to move outwardly. Theinner strut gusset plate I09 however will not move, being only looselyconnected to the gusset shackles II3 during this operation. The outwardmovement of the said inner gusset shackles II3 will likewise causeoutward movement of the extension struts I2 I, rigidly secured thereto,and of the outer gusset shackles I23, rigidly secured to said extensionstruts I2I. The outer strut gusset plate I21 during this operation willalso be loosely connected and hence will not move outwardly. After thespiders 3| have been bolted into their stressed positions (as shown inFigure 6) the bolts joining the connector fins I I I, of the inner strutgusset plates I09, to the inner gusset shackles H3, and the boltsjoining the connector fins I29, of the outer strut gusset plates I21, tothe outer gusset shackles I23 will be tightened.

The three outer strut connectors I01 are joined to the three upper strutconnectors 63 by three upper outer braces I35 and said outer strutconnectors III? are similarly joined to the three lower strut connectors63 by three lower outer braces I31.

The lower end of the'lowermost post section IN is joined to a base I39by means of a ball and socket joint I4I. Said base I39 is concave on itsunder surface and is provided with sharp downwardly extending feet I43.

' The mast (Figure 5) is supported by three guys I45 which arepreferably made of metal pipe and extend respectively from the threeouter strut connectors IITI to three ground anchors I 4! secured in theground equidistant from each other.

As shown in the drawings (Figure 5) the mast supports an antenna 85 bymeans of an extension post I5I rigidly secured to the upper end of theuppermost post section I04. Said extension post I5I and antenna 85 aresustained by three antenna braces I53 which respectively are secured attheir lower ends to the upper strut connectors 03 and are strengthenedby three nonadjustable fiat metal antenna struts I55 which extendoutwardly from the lower end of the extension post I5I and are rigidlysecured to said post and to the antenna braces I53.

The modified and more complicated form of the antenna just described(Figures 5-7) may be raised in any suitable manner. If it is to beraised as is the simpler form already described (Figure 4), it shouldpreferably be provided with the T-shaped base II (as shown in Figure 1).

While there has been described what is at pres-' ent consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims, to cover all such changes andmodifications as fall within the true spiritand scope of the invention.

What is claimed is:

1. In a mast, a vertically disposed central post, a strut system forsaid post including a spider longitudinally adjustable relative to saidpost and a stiff spider strut disposed obliquely to said post andpivotably secured at its inner end to said spider, means to adjust saidspider longitudinally relative to said post, an upper brace secured atits lower end to the'outer end of said spider strut and secured at itsupper end to the central post at a point higher than said strut system,and a lower brace secured at its upper end to the outer end of saidspider strut and secured at its lower end to the central post at a pointlower than said strut system.

2. In a mast, a vertical central post, a pair of strut spiderssubstantially concentric with said post and longitudinally adjustablerelative thereto, each spider including a like plurality of legsextending substantially radially outwardly relative to said post, thelegs of the spiders being disposed in pairs, each pair comprising a legon the lower spider and a leg on the upper spider positionedsubstantially above it, means to adjust said spiders longitudinallyrelative to said post, a plurality of spider struts pivotably secured attheir inner ends to said legs respectively so as to make up a pluralityof pairs of spider struts, each pair comprising one spider strutsubstantially above another, a strut connector secured to the outer endsof the spider struts of each pair, a plurality of pairs of braces, eachpair comprising a brace secured at its lower end to a strut connectorand at its upper end'to the central post at a higher level and a bracesecured at its upper end to said strut connector and at its lower end tothe central post at a lower level, each of said strut connectorsincluding a strut gusset plate horizontally adjustable relative to thebalance of said connector, and a plurality of I struts joining theseveral strut gusset plates.

3. In a mast as defined in claim 2, a plurality of ground anchorsdisposed about the lower end of the central post and a plurality of guysconnecting the several strut connectors to the several anchors.

4. In a mast, a vertical central post, a pair of strut spiderssubstantially concentric with said post and longitudinally adjustablerelative thereto, each spider including a like plurality of legsextending substantially radially outwardly relative to said post, thelegs of the spiders being disposed in pairs, each pair comprising a legon the lower spider and a leg on the upper spider positionedsubstantially above it, a plurality of spider struts pivotably securedat their inner ends to said legs respectively so as to make up aplurality of pairs of spider struts, each pair comprising one spiderstrut substantially above another, a plurality of strut connectors, eachstrut connector comprising a horizontal strut gusset plate and twogusset shackles slidably secured to said plate respectively above andbelow it, said two gusset shackles respectively being pivotably securedto the outer ends of the spider struts of one pair thereof, a pluralityof pairs of braces, each pair comprising a brace secured at its lowerend to the upper gusset shackle of a strut conhector and at its upperend to the central post at a higher level and a brace secured at itsupper end to the lower gusset shackle of said strut connector and at itslower end to the central post at a lower level, and a plurality ofstruts joining the several strut gusset, plates.

5. In a mast, a vertical tubular central post, two strut spidersadjustable longitudinally relative to said post, each strut spidercomprising a central internally threaded sleeve longitudinally movablewithin said post and a plurality of outwardly extending legs, said legsrespectively extending through longitudinal. slots in said central post,a plurality of outwardly extending still spider struts respectivelypivotably secured to said legs, said spider struts being disposed inpairs one above the other, the outer ends of the spider struts of eachsuch pair being pivotably secured respectively to a pair of gussetshackles, 'means for joining said gusset shackles of each pair, a bracejoining the upper gusset shackle of each pair to the central post at ahigher level, a brace joining the lower gusset shackle of each pair tothe central post at a lower level, means to move the spiderslongitudinally relative to the central post so as to move the gussetshackles outwardly from the post.

6. A mast as defined in claim 5, including struts connecting the severalpairs of gusset shackles, the connections between the struts andshackles being slidable.

7. In a mast, a central post, a strut spider longitudinally adjustablerelative to said post, an elongated brace member having its oppositeends secured to the post at two points spaced from each other, a stiffspider strut extending obliquely outwardly from said-post and pivotablysecured 8. In a mast, a central post, a strut spider longitudinallyadjustable relative to said post, a plurality of elongated, bracemembers having their opposite ends secured to the post at two pointsspaced from each other, a plurality of stiff spider struts extendingobliquely outwardly from said I post and pivotably secured at the outerends respectively to the brace members at points intermediate the endsof said brace members and pivotably secured. at their inner ends to the.strut spider, whereupon the spider may be adjusted to swing said spiderstruts and thereby increase the perpendicular distances from the post tothe outer ends of said spider struts and thereby subject the bracemembers to tension and the post to compression.

9. In a mast, a vertical central post, three strut spiderslongitudinally adjustable relative to said post, said spiders includinga central spider disposed substantially at the central portion of saidpost, a lower spider disposed intermediate the lower end of said postand. the central portion thereof, and an upper spider disposedintermediate the central portion of said post and the upper end thereof,a plurality of lower elongated brace members having their opposite endssecured respectively to the lower end or the post and to the centralportion of the post, a plurality of upper elongated brace members havingtheir opposite ends secured respectively to the central portion of thepost and to the upper end of the. post, a plurality of stiii lowerspider struts pivotably secured at their inner ends to the lower spiderand at their outer ends respectively to the lower brace members atpoints intermediate the ends of said lower brace members, a plurality ofstiff upper spider struts pivotably secured at their inner ends to theupper spider and at their outer ends respectively to the upper bracemembers at points intermediate the ends of said upper brace members, aplurality of central elongated brace members having their opposite endssecured respectively to the outer ends of the lower spider struts andthe outer ends of the upper spider struts, and a plurality of stiffcentral spider struts i2 pivotably secured at their inner ends to-thecentral spider and at their outer ends respectively secured to thecentral brace members at points intermediate the ends of said centralbrace members. y

10. In a mast as defined in claim 9 which in cludes a plurality ofground anchors and a plurality of guys extending from the said groundanchors up to the central brace members at points intermediate the endsof said central brace members. Y

11. The method of erecting a mast, of the type having a central post andthree struts extending outward from the midportion of the post'and athree cornered base having pulley means at one corner and rotatablemeans at the other two corners to allow rotation of the mast about anaxis extending through said other two corners, comprising the followingsteps? installing three ground anchors in the ground substantially atthe points where the three corners of theibase are to rest when the mastis erected,'installing an auxiliary ground anchor at a point'so that thefour anchors delineate the extremities of a cross, the distance betweenthe said auxiliary anchor and the nearest of the other anchors beingless than the distance between the base and struts of the mast,assembling the components of the mast upon the ground so that the twocorners of the base provided with rotatable means are disposed at two ofthe anchors and the struts are adjacent a point above said auxiliaryanchor and the pulley means is on the corner of the base extendingupwardly, securing a chain hoist to the outer end of the upwardlyextending strut, rum ning one free end of cable of said hoist over thepulley and down to the third ground anchor and securing it thereto,securing the other free end of cable of said hoist to a coil'spring,securing the other end of said spring to the auxiliary anchor, andoperating the chain hoist so as to pull in the first free end of cablethereof and let out the other end. I

12. In a mast, a vertical central post, a strut extending obliquely,outwardly from said post, a

brace extending from the outerend of said strut up to the post, a secondbrace extending from the outer end. of said strut down to said post,means to swing'said strut toward a more nearly horizon tal position soas to lengthen the horizontal component of said strut and therebysubject said post to compression and prestress said braces, said meansincluding a spider longitudinally movable relative to the post, theinner end of the stint being pivotally secured to said spider, and meansto move said spider longitudinally relative to said post.

ERIC A. BLACK.

REFERENCES orrnn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 125,771 Trego M Apr. 16, 1872434,639 Maxwell Aug. 19, 1890 522,817 Zerfas July 10, 1894 845,242 LeidlFeb. 26, 1907 2,176,965 Haynes Got. 24, 1939 2,267,705 Athy Dec. 30,1941 2,271,578 Woolslayer et al. -0..- Feb. 3, 1942 2,319,303 CrawfordMay 18, 1943 2,403,081 Hil qlfn .a July 2,1946

